river battle

APOC'S successful

battle against the ^vector of river blindness

Painstaking preparation, a strong team splrit, a high level of expertise and unwavering perseverance are the qualities that have allowed APOC, the Afrlcan Programme for Onchocerciasis Control, to wipe out the blackfly vector of Onchocerciasis, or river blindness, on the island of Bioko. Situated in the Gulf of Guinea ³ 2 kilometres from the

coast of Cameroon, Bioko has a total area of about 2000 square kilometres (nearly 800 square miles) and is the largest of the five inhabited volcanic islands belonging to the Republic of Equatorial Guinea. The nation's capital, Malabo, is located on Bioko's northern

coast.

For the international health community, Bioko has the doubtful distinction of being reputedly the only island ln the world where onchocerciasis is endemic. Thanks to the determination of APOC, it now merits the reputation of being, in all likelihood, the only island in the world where the blackfly vector of the disease has been eliminated and where the aim of eliminating the disease is no longer a far-fetched dream.

APOC's achievement has certainly given Presi- dent Obiang Nguema Mbasogo of Equatorial Guinea cause for enthusiasm. ^"The successful outcome of APOC's efforts to eliminate the blackfly vector on Bioko Island," he said at a

September 2010 meeting of \MHO's Regional Committee for Africa, "raises hopes ln the battle against pandemics such as Oncho- cerciasis. I awalt the application of these successful efforts to our mainland."

Clearly, in their battle against the island's onchocerciasis vector APOC and its partners are all the more deserving of praise given the

obstacles they have had to face to achieve their goal-obstacles that ^led many experts to cast doubts on the prospects of success.

For the 250 000 Bioko islanders, APOC's achievement already means the hope for a

future free from the relentless biting of the moutoumoutou, as the blackfly is knoum Iocally, and from the parasitic worms

it

transmits. Freedom from the intense itching, from the need to scratch the skin, often to the bone. Freedom from unsightly skin wheals and skin discolouring. Freedom, at last, from the blindness that gives the disease its name.

And freedom, too, from the need to abandon the villages and fertile land bordering rivers where the blackfly breeds and bites.

Certainly, in Bioko the particular species of blackfly that carries the onchocerciasis worm-Simul ium yahe nse Bioko form-is highly active: in the rainy season, from May to December, when rivers are fast-flowing

and favourable to Simulium breeding, Bioko inhabitants may each suffer, on average, more than 500 bites a day from the blood-seeking female blackfly. This "nuisance factor" has made life difficult, lf not intolerable, for many of the islanders.

My mother

says she can

hardly rentenlber a time when her

skrn

was not itchrng.

To

her it

seemed sl'Le

had

rtchecl

all her life,"

recalls a young girl Iiving on

the island.

"Over the

years the constant scratclting got

worse

and

cctused

a lot of bleedincl that led

tct

very ugly

scars

and wounds on her

legs

and buttocks. Iler

hLtsbancl was

ashamed of her and drove her and

r.ts

chtldren away. With

nowl'tere

to go

...she

fled tlte vrllage artd took

Lrer

chilclren vvith

her.

So ingrained had the blackfly vector become over the centuries, that the ^prospect of wiping it out on the island seemed impossible.

Indeed, in the late 1990s, before the APOC campaigns began, many experts were sceptical. They pointed to the rugged, densely vegetated terrain, that prevents access to about 90% of the island's area. In this terrain, ground-based teams, they said, would be unable to collect information about the rivers, such as flow rates and other parameters, and about the blackfly vector's breeding sites. The only alternative, they said, would be to use helicopters to locate river breeding sites and then to spray the rivers with larvicide but these activities would surely be hindered by the thick forest canopy.

Luckily, there were also a few hardy optimists, who countered with positive arguments.

Supporting the optimists, for example, was the geographical isolation ofBioko ^Island.

Reinvasion by blackfly vectors from elsewhere would, they reasoned, be unlikely because the island is at least 40 kilometres away from the nearest sources of reinvasion in Cameroon.

It is aiso out of reach of the prevailing winds that might carry the vectors. Moreover, there is only one onchocerciasis vector species in

Bioko, which is different from the species

(5. squamosum andS. damnosum)thal predominate in Cameroon. A further positive factor i.s that only relatively small amounts of insectlcide would be needed to spray on the rivers since few rivers flow in the dry season and those where spraying is required are short (about three to four kilometres long).

Evidence to clinch the issue was clearly needed.

A series of exploratory activities, therefore, was undertaken in the Iate 1980s, followed in the 1990s by exhaustive studies carried out by scientists from institutions in Europe and others working for the OCP, or Onchocerciasis Control Frogramme in West Africa. (The OCP was launched in 1974 and was stili conducting Iargely successful insecticide spra)nng

campaigns against the Simu/ium vector in

seven of the eleven West African countries in its mandate.)

Exploratory activitles included the following:

- 1989 -

An epidemiological survey covering 1723 Bioko islanders from 12 vlllages found that

76% of these inhabitants were infected with

onchocerciasls. The disease was clearly a serious pub11c health problem on the island.

Left Bulk catches by trained villagers.

Right: National team of the ONCHO Programme.

- 1996 -

An entomoiogical survey, conducted rn Bioko under the aegis of APOC (launched the previous year) concluded that 52 rivers totalling 1020 kilometres would need to be treated with larvicide in order to eliminate the vector from the island.

- 1999 -

Tests by APOC and former OCP specialists showed that the blackfly larvae on Bioko were sensltlve ^(i.e. vulnerable) to the larvicide temephos and would be effective in the river flow condltions prevailing on the island during the dry season, when larviciding activities would be undertaken.

- 1999 -

An environmental impact assessment showed that a larvicidal campalgn using temephos would not cause significant damage to the environment, including fish, shrimps and other creatures not targeted by the campaign.

Simulium vector

Despite the doubts stlll being voiced in some quarters of the onchocerclasis community, in 1998 APOC decided to Iaunch an all-out attempt to eliminate the vector from Bioko Island.

The battle unfolded in four distinct stages.

Stage ^1:

Preparation

Preparatlons for the elimination campaign were carried out between 1999 and 2000.

They included the setting up of blackfly collection points to monitor vector biting rates and provide basellne data for subsequent activities. Local entomology technicians were trained in the field work needed for

a campaign to eliminate the vector, such as collecting and identifying the Simulium vectors at the different stages of the insect's Iife-cycle and examining them for ^larvae of the Onchocerca volvulus worm that causes onchocerciasis.

Stage 2: Ground

larviciding trial

A large-scale larviciding trial using ground- based application of temephos to previously identified Simulium breeding sites was carried out for five weeks from 12 February 2001

throughout the northern ^(more accessible) part of the island. After the five weeks, blackflies were

stil

^active in several areas and the trial was halted. Ground larviciding was clearly not reaching enough blackfly breeding sites to eliminate the vector.

Stage 3:

Initial ground-plus-aerial larviciding campaign

Plans were made to Iaunch a two-fold attack on the blackfly, using not only ground operations but also sprayrng from aircraft.

Preparations for this campaign took up most of 2002. They included:

.

Time-consuming paperwork to obtain permits allowing a hired helicopter fltted out with sprayrng and hlgh-tech commu- nications equipment, and spare parts, to fly

over Nlgeria from its base in Togo in order to reach Equatorial Guinea.

.

Paperwork to set up a temporary base in Malabo and to use the helicopter for spray- ing in Bioko Island.

Left: Ground larviciding. Rtght: Prospection of breeding sites.

.

Yet more paperwork to ailow a Cessna aircraft to be used to transport technlcians, mechanics and other campaign staffbe- tween Malabo and Togo.

.

Training of pilots and Equatoriai Guinean entomology technicians for the intricately precise and often dangerous flying mis- sions over gorges and ravlnes sometimes hidden by a thick forest canopy and to do so

while mapping breeding sites and spraying Iarvicide.

Large scale aerial and ground larviciding operations were conducted from February to May 2003. By early May, Simulium biting rates had dropped to zero and no blackfly Iarvae could be found in any breeding site that had been sprayed. Hopes ran high that these results would be sustained and APOC's optlmism vindicated. But no, within ^a few months the vector had reappeared, mainly in the northern Bioko mountains. Seemingly, a few breeding sites had been missed by the Iarviclde sprayrng sorties.

I

I

I

Stage 4:

Final ground-aerial larviciding campaign

Disappointment at the unsuccessful 2003 campaign seemed to conflrm the pessimists.

But it only heightened the determination of

APOC and its partners, who decided to mount

a f.nal, last-ditch attempt.

Preparations for the final campaign occupied most of 2004. Since the first female blackflies to reappear after the 2003 operations were sighted in the northern mountains of

Bioko, that is where APOC concentrated its preliminary research efforts to identify the breeding sites that may have been missed in

2003.

'iI

i

From lanuary 31to May 15, 2005, all known biackfly breeding sites in the island received weekly applications of larvicide by helicopter or from the ground or by both routes. About 120 breeding sites per week were sprayed on the ground simultaneously ^by two teams, each working in a different circuit, in order to

cover all known breeding sites on the island.

During the 15-week spraying period, blackfly collection and dissection continued daily to determine vector density and O.

volvulus transmission rates and to check for possible blackflies that may have eluded the elimination efforts. Monitoring of all breeding sites continued for nine months after

cessation ofspraying activities and produced no evidence ofresurgence ofthe vector.

60000 5000o a0@o 30000 20 000 10 000

liy March 5, rlili.lt,lrlur'k11y biting lr:rd lt'lrserl

t lrrou ghout tirt' Lsl:r rrd. Irrom Alrrr ¹ ort,"n,rt rr.l s.

entornologrlr I sLr rver il.ince tet nr 's i rr r r nrl no rnore brtrng [rlrrcktlres and no ]lrrv,ri' ,lr :rnV of lire knor,vn Irlur kfly breedingl sLter. SLni-e then a welL trarned tearn of local BLoko ti'r hntcians has been rrrplr:rrtt':nttng a long terrn

surverll,rrrr e prograrnme set upr Lry AI']OC and its partrrers. f lre team s monrturrnq actrvttrc's havc- forurd 11o rrver bhnrlrress vec tors tc ilatc In May, 1()06, ;r WFIO mectrng rn Burklna FasL)

stiprrlatcd that the vectot coulrl be declarerl clrrnLnated after ih.ree yeu rs wlthout evrdcnr:c of thc blackfly Today, rnore than six years after tlie last blackfly r,r"':rs spolted, the veltor cun br'well and trrrly t:onsr,i..r..d elrrnrrr.rtcLl.

I' rt vtgtl.rnce cor tu lre ^.

In Broko itst:11, tlie rrrood rs positrve Mlrrry crf

the rslanders now tell their youn6i clrildren stortes :rbrrLrt

t\t'

rrtoutour'nouIou which once roamed f reely across the rslarrrl [rnnurng drstress, blrnrllng drsease, and socLal and econornrr: rlesolatron to

tlrl

rsiurrrl. Tod:ry, garcleris urrtl f arrnland are {lorrrjshrng on the banks o1 rLvers that people hud ulrandoneri Ln

fear rrf th.. blackflv

For AI'()( urrd rts partner.r, one battle has,

lo all intents and puryrr,ses, trcer', r,von.'fnrr:, tlrc battlc was fought on a relatrvel,; snrall

isllnrl Yet APOC':, achrcverni:nt has far r--rrlcr irn1r)rr etion-< that rcvcrIrcnitc well Lre'yund Hroko For a1l African loL.rntrres strLrggilirig to rrrl themselves rrf rr,,,r:r blLrLdncss, it gives lrope that the ^job

lln

bt- done, desprtc .rlrnost

i nsrrrmourtta b1c otrst acles "Todry," savs I)r Luls Gomes Su rnbo, WHO Regrona I Drrcctor for Afnca, "APOL is a pubhc health success story that rs provrrlrng relref to mrllions of AfrLcan people ^"

A story that ^slrrlws lvhat can trc ircr ornplished with ^{r a} reful plannrng, tearn sprrit t:xperttse and ;rersevera nce.

--1() () ()

3

; .: ,: l

a